As schematically illustrated in FIG. 1, a limiter 10 is generally used in a receiver chain 1, downstream from a receiving RF antenna 20 and upstream from an amplification stage 30 and a processing stage 40. The amplification stage 30 includes at the input, a low noise amplifier 32, a so called LNA (low noise amplifier). The function of the limiter is to protect the LNA amplifier from high power signals received by the antenna.
Such a limiter is also used downstream from an LNA amplifier robust to high power signals, in order to protect the downstream portion of the receiver chain, for example components of the processing stage which would be sensitive to too high power levels, such as coders.
More generally, such a limiter is used in any RF transmission/reception chain requiring, in one point or in another, a limitation of the maximum power delivered at the input of a sensitive component.
Presently, limiters are generally made from PIN diodes, as the latter provide good power handling.
According to a first embodiment of a limiter of the state of the art, the PIN diodes are placed in a head-to-tail configuration. In FIG. 2, the limiter 100 includes two pairs of diodes 102, 104 and 112, 114, the diodes of each pair being placed head-to-tail. With such a configuration it is possible to clip the positive half-alternation and the negative half-alternation of an input signal, beyond a power threshold P0.
According to a second embodiment of a limiter of the state of the art, the PIN diodes are placed in parallel. In FIG. 3, the limiter 200 includes three diodes 202, 204, 206 in parallel. Such a configuration gives the possibility of clipping the input signal from a power threshold P0.
The threshold P0 for triggering the limiter is mainly related to the type of PIN diodes used and to their direct current (DC) characteristics. For example, in FIG. 4 representing the output power Pout of the limiter 100 versus the input power PIN, the threshold P0 is of about 14.75 dBm.
However, the threshold P0 cannot be adjusted. This lack of reconfigurability of a limiter does not allow production of a standard limiter and its use in different applications, operating in the same pass band.